Coating material recovery medium and process



fl- 1, 1943. s. e. SAUNDERS ETAL 2,323,399

COATING MATERIAL RECQVERY MEDIUM AND PROCESS Filed Sept. 10, 1941 BY f/arr g fi/brr '50 ATTORNEY 4 umrep STATES PATENT OFFICE coarma MATERIAL nncovsar MEDIUM sun raocuss Seymour G. Saunders, Bloomfield Hills, and Harry Morrison, Detroit, Mioln, assignors to Chrysler Corporation, Highiand Park, Mich, a corporation of Delaware Application September 10, 1941, Serial No. 410,268 1 Claim. (01. 106-287) This invention relates to an improved appapatents. when the particles of excess sprayed ratus and process for reconditioning recovered coatink material are precipitated or otherwise desolids of excess sprayed coating materials which posited in such form that they collect as a sludge have been collected in a recovery medium malnat the bottom of a settling tank or accumulate 1y comprising water. 5 in scum-like formation on the surface 0! the liq- More particularly, the invention pertains to a uid oi the tank, depending upon the nature of the process for the removal of water or other recovcoating material and recovery medium. The term ery medium irom recovered excess sprayed coat- "soli s us herein nd as nv nti nally. ing material whereby the latter is conditioned for employed in the surface coating art reiers to reuse. in those. portions oi. suriace coating material which One of the main objects of the invention is remain, either in their initial'or chemically alto provide an eihclent and economical processand tered term, in a normally set deposit of such apparatus for removing recovery medium from coating materialainciuding the non-volatile vehicollected excess sprayed coating material which cle and pigment.

has been collected in accordance with the dis- 1!: In the practice of our improved process and closures in Patents Nos. 2,086,514 and 2,208,646 apparatus for reconditioning the above collected issued July 6, 193'! and July 23, 1940, respectively studge, the latter is removed trom the settling for an improvement in coating material recovtank and conveyed in a 'bucket lit by conveyor ery process. mechanism. generally designated by the rhuneral Another object o! the invention is the provision H. to a hopper 12 which discharges the sludge 01 a process or this character which operates into theinterior of a mixing tank generally desemciently at maximum temperatures far below isna y h n er it T e m x tas the boiling temperature or water. is provided with a steam Jacket ll or other suit- A further object of the invention is the proable means by which it may be heated. Steam vision of a process of this kind during which the is admitted to the jacket through an inlet pipe solids'are incorporated for reuse'in the vehicle or ii, circulated therethrough and discharged from solvent in which such coating material solids are the jacket through an outlet pipe it, Disposed conventionally used. in the inner chamber I] of the mixing tank are A still further object oi! the invention is the suitablemixers II which are driven by a motor utilization in a process at this kind or the same 2:) II. An auxiliary solvent container 20 is consolvent loathe purpose or extracting occluded nected by a pipe II with the inner chamber i'l water from the solids as is conventionally used 91 the mixing tank tor the purp se ipplying'a in reducing the latter to a sprayable consistency. suitable solvent thereto. The sol ent employed An addi ional object or the invention is the in this process preferably comprises-the same provision in a process or this character for the solvent or vehicle which is conventionally used reuse, in a continuous repeating cycle, of the in the finished coating material of the type being fraction of solvent utilized to extract the ccoperated upon. High solvent naphtha, toiuol, eluded water tom the solvents. mixtures of tol l and naphtha, xyiol, and mix- An illustrat ve embodiment o! the invention is tures of naphtha oi dlilerent boiling points are shown inthe accompanying drawingin which the 40 examples of suitable solids which ma be used figure is a diagrammatic side elevational view, for this purpose. A small amount or butyl alcohol pa y in ion. of apparatus for separating may be added to the solvent tor the p rp se or recovery medium from recovered solids of excess protecting certain resins ainst ri tal isprayed coating material in accordance with the feet by heat durlna the distillation stei The invention. I solvent employed should have the property or In general, excess sprayed coating materials mixing with water to rorm a mixture which upon are collected by directins the discharge Irom a heatlnz is vaporized and distilled from the mixspray gun which misses the work upon a curtain ing tank It in the form of a mixture of solvent or. spray of liquid, such as water. in which is and water vapor.

included ingredients that have for their purpose to The upper end portion 0! the inner chamber the rendering of the collectedparticles or excess II or the migdm tank it is connected by a consprayed coating material non-adhesive to the dull: 2: with a combined condenser and settling walls 01 a structureinwhich they are confined. tank unit generally designated by the numeral Various examples of suitable recovery mediums 28 which has an enlarged lower settling tank or this kind are set forth in the above mentioned portion and a smaller diameter oondensina chamher It disposed thereabove. A cooling coil 26 is provided in the condensing chamber it and connected with a source of cooling water (not shown) by a pipe 21. When the mixture oi water and solvent vapors enters the condensing unit 23, it flows upwardly into the condensing chamber 25 where it is cooled and precipitated. The condensate thus formed drips into the settling tank 24 and separates into two layers, the solvent accumulating in. the upper layer and water in the lower layer. An overflow pipe 28 leadin from the upper end portion 01' the settling tank 24 conveys overflowing solvent from the latter tank to the inner chamber l1 oithe mixing tank I3 50 as to continuously replenish the solvent content in the latter chamber. The water accumulated in the bottom of the settling tank 24 may be drained oil and discharged into a sewer through an outlet pipe 28.

In order to facilitate removal of water from the sludge deposited in the mixing tank i3, at a temperature substantially below the boiling point of water, the pressure in the mixing tank i3 above the liquid level therein and the pressure in the condenser chamber 25 is maintained below i atmospheric pressure by applying a vacuum which is produced by a suitable vacuum pump mechanism generally designated by the numeral 30. The vacuum pump is connected with the upper end portion the condensing chamber by a pipe II and the vacuum is applied on the interior of the mixing tank i3 through the vapor outlet conduit 22.

The inner chamber ll of the mixing tank I3 .is provided with a coating material outlet 33 which is connected by a pipe 34 having a valve 35 therein with a storage tank 36. The storage tank 36 is connected at its upper end with the vacuum line 8| by a pipe 31 having a valve 38 therein. By virtue of this connection between the storage tank 36 and the vacuum line \oi, the vacuum applied on the condenser and mixing tank may be utilized to withdraw dissolved coating material solids which have been thoroughly mixed with solvent and from which occluded water has been extracted from the chamber ll of the tank It and to deliver it to the storage tank. This may be accomplished by opening valves 35 and 88. When the valves 35 and 38 are closed, the coating material contained in the tank 36 may bsuppliied for reuse or for shipment in containers through an outlet pipe 39 having a control valve l0 therein.

The viscosity 0! the reconditioned coating material withdrawn grom the tank I! may be predetermined by coii'trolling the amount oi solvent added but it is preferable to maintain the viscosity of the coating material discharged from the tank I! at a much higher viscosity than that normally used in, the application oi. coating material. This product may be thinned to a desired viscosity by the further addition of solvents and vehicles by the user.

In the practice of the foregoing process, the occluded water content of the sludge delivered to the apparatus by the bucket l0 and any water remaining therein after a rough settling operation of the main bulk of the recovery medium from the sludge is removed therefrom and the sludge is simultaneously incorporated in a homogeneous mixing operation in the solvent which later serves as the vehicle for the reconditioned coating material solids. The temperature required to drive off the water is much lower than that which has a detrimental effect upon the coating material. That portion 01 the solvent which was utilized to extract water is collected and returned to the tank l3 for reuse in a continuous and repeating cycle.

Although but one specific embodiment of the invention is herein shown and described, it will be understood that various changes in the sequence of operations, steps and materials employed may be made without departing from the spirit of the invention.

We claim:

The method of reconditioning recovered solids of excess sprayed coating material and separating therefrom residual water introduced during its collections which consists in dissolving in a mixing chamber said water contaminated solids in a liquid solvent having a lower boiling point than water and of the same kind as that normally used in the application of the coating material, distilling said water togetherwlth a portion of the solvent in said mixing chamber from said solution under heat and vacuum at a temperature below the boiling point of water, condensing the resulting distillate, separating the water and solvent of said condensate, returning said condensed solvent to said solution of coating material solids while the latter is undergoing water extraction in a continuous process for repetition of 'said vacuum distillation water removal, and periodically removing from said mixing chamber portions of the resulting solution of water-free coating material in said normally usable solvent and replenishing said chamberwith water contaminated solids without inte rupting said vaccum distillation water removal operation.

SEYMOUR G. SAUNDERS. HARRY MORRISON. 

